Microsoft's Outlook Blog reported that there was an outage to Outlook.com, Hotmail.com and SkyDrive services on Tuesday, March 12 at 1:35 p.m. PDT. The interruption cut off access to these services for some users.

According to Microsoft, the cause of the outage was a temperature spike in the physical region of one of its datacenters. At the time, Microsoft had been performing a firmware update on a core part of the physical plant, which led to the increased temperature.

This spike caused the datacenter's safeguards to jump into action, which prevented access to Outlook.com, Hotmail.com and SkyDrive services.

From there, a combination of both human and software mediation helped bring the services back online throughout the day. The services were fully restored on March 13 at 5:43 a.m. PDT.

"Outlook.com left preview a few weeks ago, and as part of that, we shared that we'd start to upgrade the hundreds of millions of people using Hotmail to the new, modern Outlook.com experience," said the Outlook Blog. "We had done multiple pilots during the preview period and learned a ton. Overall, the upgrade has been going very well--people have upgraded much faster than we had expected. The vast majority of people using our services have had a smooth experience during this time and are enjoying the new Outlook.com experience. That said, we had an issue yesterday and wanted to provide you with a deeper look at what happened.

"We do want to sincerely apologize to anyone that was unable to access their email during the interruption. Outages are something we take very seriously and invest a significant amount of our time and energy in doing our best to prevent."